In-well flow meters are used in well systems, such as hydrocarbon-bearing wells, to measure fluid characteristics of a well fluid, such as flow rate and fluid type to determine pressure, temperature, and viscosity, among others. An in-well flow meter to measure fluid density includes several sensors and uses several math algorithms to interpret complex fluid flows of a fluid in a well system. An example of such an in-flow well meter is a venturi meter coupled with a nuclear source and detector to measure fluid density. Sometimes, a flow meter is placed on or is integral to a well tool disposed in a wellbore to measure fluid characteristics of the wellbore fluid during well drilling or production operations.